As is known, the most recent mountaineering ski boots basically comprise: a rigid shell made of plastic material, which is shaped substantially like a shoe so as to accommodate the foot of the user, and has the lower part specifically structured to be fixed to the back of a downhill ski or the like by means of a suitable mountaineering ski binding device; a rigid cuff made of plastic material, which is shaped so as to embrace the lower part of the leg of the user from behind, and is hinged to the upper part of the shell so as to be able to rotate about a transversal reference axis, which is substantially perpendicular to the vertical midplane of the ski boot, and is also locally substantially coincident with the articulation axis of the ankle; and an innerboot made of a soft and thermal-insulating material, which is inserted inside the shell and the cuff, and is shaped so as to enclose and protect both the foot and the lower part of the leg of the user.
The mountaineering ski boots mentioned above are additionally provided with shell closing means and cuff closing means, both manually operated. The shell closing means are structured so as to be able to selectively close/tighten the shell on the foot of the user, thus to immobilize the foot of the user inside the shell, or rather the innerboot. The cuff closing means, in tune, are structured so as to be able to selectively close/tighten the upper part of the cuff on the leg of the user, thus to immobilize the leg of the user inside the cuff, or rather the innerboot.
Finally, the mountaineering ski boots also include a manually-operated cuff locking device which is traditionally placed in the area above the heel of the boot, and is structured so as to be able to selectively and alternately lock the cuff to the shell in a rigid manner thus to prevent any pivoting movement of the cuff on the shell; or fully release the cuff from the shell so to allow the cuff to freely pivot on the shell.
In the most modern mountaineering ski boots, the cuff locking device is basically made up of an oblong movable arm which is butt hinged to the cuff above the heel of the boot so as to be able to rotate while remaining on the midplane of the boot, and is movable to and from a locking position in which the arm extends downwards skimming the outer surface of the cuff and places its distal end in abutment against the rear of the shell, more or less in the area of the heel; and an elastic member acting on the arm so as to push and elastically retain the arm alternately in the locking position or in an unlocking position in which the arm is rotated upwards so as to raise and move the distal end of the arm away from the shell. The distal end of the arm, in turn, is structured so as to be able to firmly couple to the shell at a predetermined anchorage point, so that the arm can prevent any oscillation of the cuff on the shell.
In most mountaineering ski boots currently on the market, the elastic member consists of a small leaf spring which acts directly on the proximal end of the arm.
While working excellently, the leaf spring is not able to apply a great elastic force on the arm, and this can unfortunately cause some problems when the user actuates the cuff locking device under particularly adverse environmental conditions.
Experimental tests, in fact, have shown that in some cases the leaf spring fails to apply an elastic thrust sufficient to allow the distal end of the arm to cut through the snow that traditionally accumulates on the rear of the shell, and reach the anchorage point.